The present invention relates to an electrophotographic sensitive member capable of enhancing a photosensitivity on both a short wavelength side and a long wavelength side and a charge acceptance and thus suitable for a plain paper copying machine.
Recently, the stabilized operation characteristics and durability have been required for an electrophotographic sensitive member carried on the instruments, such as high-speed copying machine and laser beam printer, with an active development of said instruments. Amorphous silicon has been watched with interest for this requirement in view of superior abrasion resistance, heat resistance, antipollution property, photosensitive characteristic and the like thereof.
A multi-layer type photosensitive member as shown in FIG. 1 has been proposed for an electrophotographic sensitive member formed of amorphous silicon (hereinafter called a-Si for short).
That is to say, referring to FIG. 1, a barrier layer (2), an a-Si carrier-generating layer (3) and a surface protective layer (4) are formed on an electrically conductive substrate (1) formed of aluminum and the like in this order, the barrier layer (2) being formed for preventing the carriers from entering from the substrate (1) and lowering the residual potential, and the surface protective layer (4) being formed of highly hard materials to enhance the durability of the photosensitive member.
However, such the a-Si photosensitive member exhibits the higher photosensitivity on the long wavelength side. Accordingly, in the case where this photosensitive member is carried on the plain paper copying machine (hereinafter called PPC for short) with a white color, such as halogen lamp, as a light source, it is inferior in reproducibility for a wavelength zone near to red color. In order to solve such the problem, a filter is used to cut infrared wavelength lights but this leads to the reduction of the intensity of a light, which is incident upon the photosensitive member, and as a result, the photosensItivity of the photosensitive member itself is apparently lowered.
In addition, the high charge acceptance is one of the desired characteristics required for the a-Si photosensitive member in addition to the above described photosensitivity. In the event that such the desired characteristics were achieved, a high image concentration Is obtained and the degree of freedom in the design of the developing system of the copying machine, whereby obtaining an easily usable electrophotographic sensitive member.